The present invention relates to a technique for recording/reproducing picture information, in particular still picture information, on/from a recording medium.
FIG. 2 shows an example of the conventional arrangement of information files that are stored on an optical disk, such as a DVD (Digital Versatile Disc), where moving picture information is recorded. In the information file structure shown in FIG. 2, a directory DVR is formed on the optical disk. Each information file is recorded under this directory.
In FIG. 2, the info.dvr file 201 is a file where information such as the number and filenames of play lists under the DVR directory is written. The menu.tidx file 202 is a file where information such as the sizes and information amounts of thumbnails to be used in menus is recorded. The menu.tdat file 203 is a file where thumbnail picture information to be used in menus is recorded. The mark.tidx file 204 is a file where information such as the sizes and information amounts of thumbnails associated with mark positions are recorded. The mark.tdat file 205 is a file where thumbnail picture information to be used at mark positions is recorded. Play list files 206 are files where marks and other information specifying in what order and what parts of picture information are to be reproduced are recorded. Clip information files 207 are files where information such as play start points in stream files and their packet positions is recorded. Stream files 208 are files where such packets as picture information and sound information are recorded.
With respect to the stream files 208, picture information is compressed according to the MPEG2 standard, which is one of the standard picture information compressing techniques, and the compressed information is converted into a stream file before being recorded. MPEG2 provides an excellent ability to compress a large amount of information not only to NTSC-format picture information, but also to HD (High Density) picture information, such as Hi-Vision. The amount of information in original picture information can be compressed to about one tenth or one fiftieth. For example, picture information in the NTSC format is compressed to about 6 Mbps, while HD picture information is compressed to about 20 Mbps. In both cases, MPEG2 can attain a sufficiently high picture quality. Picture information compression by MPEG2 is widely used in such applications as accumulation of picture information on DVDs and digital broadcasting.
With respect to the clip information files 207, in the same manner as described above, picture information is compressed according to the MPEG2 format before being recorded. The MPEG2 system compresses picture information based on correlations between adjacent pictures. More specifically, if there are portions which do not change between adjacent pictures, information relating to these portions is not transmitted again, and the last picture information received is used as it is for these portions. However, this imposes a drawback in that not all picture information elements can be reproduced by decoding such picture information, only the changed portions of which were encoded. After such an operation as fast forward or skip, play can be restarted only from those pictures in which all picture information elements were encoded.
Generally, when picture information compression is performed according to the MPEG2 standard, picture information is divided into groups, each comprising about fifteen pictures. Each of these groups is called a GOP (Group of Pictures). Play from the top of a GOP allows immediate reproduction of picture information.
In the clip information file 207, the packet position of the top of each GOP is recorded with the time (corresponding to the Presentation Time Stamp value) indicating when its picture information was encoded. This makes it possible to easily find a play start position when a search or skip operation is performed.
Clip information files 207 are associated with stream files on a one-to-one basis. If a clip information file designated 01000.c1pi is recorded in association with a stream file designated 01000.m2ts, these files can easily be recognized as being associated with each other.
With respect to the play list files 206, information recorded in each play list file lists parts of stream files which are to be played in the specified order. FIG. 3 more specifically shows the information structure of the play list files. In a play list file, the version_number entry indicates the version of the play list. The PlayList_start_address entry indicates where the play list information is recorded in the play list file. The PlayListMark_start_address entry indicates where the play list mark information is recorded. The MakersPrivateData_start_address entry indicates where the maker's private information is recorded. Note that each play list contains information about one or more play items, indicating what parts of stream files are to be played.
An example of, the play list mark information will be described in detail with reference to FIG. 7. The length entry indicates the information length of the play list mark information. The number_of_PlayListMarks entry indicates the number of play list marks. The mark_type entry indicates the type of the play list mark. The mark_name_length entry indicates the length of the play list mark's name. The ref_to_PlayItem_id entry indicates the number of the play item associated with the play list mark. The mark_time_stamp entry indicates the time when the play list mark was marked. The Entry_ES_PID entry indicates the packet ID of the ES (Elementary Stream) of the play item associated with the play list mark. The ref_to_thumbnail_index entry indicates the number of the thumbnail associated with the play list mark. The mark_name entry stores a character string representing the name of the play list mark.
An example of the stream management structure of moving picture information will be described with reference to FIG. 13. As shown in FIG. 13, a stream is composed of plural titles and a title is composed of plural chapters. Each chapter is composed of plural scenes. In many cases, each scene is constituted by moving picture information that has been recorded continuously until recording is stopped after having been started.
With reference to FIG. 7 and FIG. 13, the types of play list marks will be described. Each play list mark may have be any of one of several identifiable types; for example, a title mark indicates the top of a title, a chapter mark indicates the top of a chapter and a skip mark indicates the top of a scene.
With reference to FIG. 8, an example of how the play list information, play item information, clip information, stream files and play list mark information are mutually associated will be described. Each play list includes one or plural play items. In this example, two play items 802 and 803 are shown a part of play list 801. Each play item specifies what part of what stream file is to be played by designating the corresponding clip information's filename, STC_sequence number, start time and stop time. More specifically, the play item 802 is associated with an area 804 of a stream file.
Each play item may be associated with a different stream file. Reference numerals 806 and 807 respective indicate positions where play list marks are recorded. Actually, these play list marks are recorded in the play list information and are converted to packet positions in the actual stream file by using the clip information. (For example, see Japanese Patent Laid-Open No. 2003-123389.)
The above-mentioned technique assumes that moving picture information is recorded and reproduced using MPEG stream files. However, it is necessary to record/reproduce still picture information as well as moving picture information. In addition, unlike moving picture information, when still picture information is to be reproduced, it is desirable to allow each still picture to be accessed easily. When reproducing a plurality of still pictures from a recording medium, the user is required to perform operations for such purposes as to switch to the previous or next picture.
Since the recording/reproducing of still picture information is not taken into consideration in the conventional recording and reproducing apparatus, however, the apparatus can not operate properly in response to the above-mentioned operations by the user. In addition, a method for displaying still picture information while outputting sound information continuously as BGM (Background Music) has not been taken into consideration.
It is an object of the present invention to solve the above-mentioned problems, that is, to allow still picture information to be easily selected and reproduced and to provide a user-friendly reproducing technique.